drm/amd/display: Return max resolution supported by DWB

mode_config's max width x height is 4096x2160 and is higher than DWB's
max resolution 3840x2160 which is returned instead.

Cc: stable@vger.kernel.org
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_wb.c

@@ -76,10 +76,8 @@ static int amdgpu_dm_wb_encoder_atomic_check(struct drm_encoder *encoder,
 
 static int amdgpu_dm_wb_connector_get_modes(struct drm_connector *connector)
 {
-	struct drm_device *dev = connector->dev;
-
-	return drm_add_modes_noedid(connector, dev->mode_config.max_width,
-				    dev->mode_config.max_height);
+	/* Maximum resolution supported by DWB */
+	return drm_add_modes_noedid(connector, 3840, 2160);
 }
 
 static int amdgpu_dm_wb_prepare_job(struct drm_writeback_connector *wb_connector,